We’ve already seen a couple of useful calculator apps for the Apple Watch, but the most recent one, released today, arguably has the coolest interface of them all. Geek Watch takes the design and interface of the classic Casio calculator watch and puts it on the Apple Watch.

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As you can see in the screenshots above, there’s no Casio branding on the interface due to legal obligations, but nearly everything else is directly inspired by the popular classic calculator watch. One issue, as noted by TechCrunch, is that since Apple hasn’t yet enabled custom watch faces on the Apple Watch, there are some annoying borders around the calculator that prevent it from being fully immersive.

Geek Watch is available on the App Store now for $1. At this point, it seems to be more of a novelty purchase as other calculator apps for the Apple, such as CalcBot and PCalc, offer more functionality, just with less nostalgic interfaces. A video showing off Geek Watch can be seen below: